This invention relates to a process and apparatus for producing energy through the fusion of atomic nuclei and more particularly relates to a novel process and apparatus wherein the particles which are to enter into the fusion reaction are contained in counter-moving, relatively low energy beams in vacuum without a plasma.
The production of energy in a fusion reaction is well known although a successful self-maintaining process has not yet been carried out. The fusion reaction for the production of energy is desirable since it employs readily available fuels, particularly isotopes of hydrogen, and since fusion energy is safe and environmentally acceptable. The process is safe because very small amounts of particles, particularly deuterium and tritium, react at any instant so that a large uncontrolled release of energy is impossible. Moreover, fusion is inherently safe since the fusion process is quenched in response to any failure of the confinement system.
In order to obtain a self-sustained fusion reaction it is known that the so-called Lawson criterion must be satisfied. The Lawson criterion places inherent requirements on fusion systems such as the pulsed Tokamak system so that a power density in a plasma of deuterium and tritium must be about 18 kilowatts per cubic centimeter while a magnetic confinement field is required for the creation of the magnetic bottle which confines the plasma in a magnetic field of about 140 kilogauss. These requirements are extremely difficult to fulfill and explain the long delay in completion of, and high capital cost of Tokamak type equipment which will be capable of carrying out a self-sustained fusion process.
More specifically, some of the difficulties with successful operation of devices such as the Tokamak Fusion Test Reactor are as follows:
1. It is necessary to have a sufficient density of hydrogen isotopes such as deuterium or tritium to permit the fusion reaction. However, this density is difficult to maintain eletrically because it is difficult to obtain a sufficient voltage gradient in the plasma to effectively add energy and thus increase the temperature of either the positive ions or the electrons. All attempts to obtain an electrical gradient cause an electron current to flow but do not add very much energy to the positive ions which are the particles which must have high velocity in order to obtain the collisions needed to produce the fusion reaction.
2. Since the deuterium or tritium gas density should be relatively high, it is difficult to purge gas impurities from the plasma container. The existence of these impurities reduces the probability of fusion reaction between particles since they absorb energy from the isotope ions without contributing to the possibility of a fusion reaction. The impurity problem is well known and is complicated by the fact that the energy density in the plasma must be extremely high, causing the vaporization of many solids which are used in constructing the apparatus.
3. The positive ions of deuterium and tritium which are expected to combine are all positively charged and therefore repel each other in the plasma. Consequently, it is difficult to obtain a collision which causes a fusion reaction rather than an elastic collision. Several thousand collisions are required at the correct velocity vector direction and magnitude in order to cause a single fusion reaction. In the past, attempts to solve this problem were simply efforts which add to the density and energy of the plasma to cause more collisions even though the probability of a fusion reaction was extremely low because of the random velocity vector directions of the particles.
In order to add energy to the plasma, various heating methods are now being used in Tokamak machines. These include ohmic heating and neutral beam heating. Ohmic heating does not produce ion velocity vectors in the correct directions within the plasma to cause high energy collisions because when high fields are produced, the major velocity components are mostly in the same direction as that caused by the ohmic heating current flow. Consequently, ohmic heating of the gas encounters great difficulties of application. The use of neutral beam heating of the plasma and radio frequency heating are helpful but these require extremely large capital investment and complex equipment for the reactor.